1. Technical Field
An aspect of the present invention relates to a high voltage transformer, and more particularly, to a slim-type high voltage transformer in which a plurality of protruding grooves in place of a bobbin are formed in the interior of a case, and primary and secondary winding coils are mounted to the protruding grooves, thereby minimizing the height of the transformer.
2. Description of the Related Art
Recently, liquid crystal displays (LCDs) have been widely used not only for personal computers and notebook computers but also for office automation equipments such as photocopiers and portable devices such as cellular phones and beepers because they can be miniaturized as compared with cathode ray tubes (CRTs).
Since an LCD is not a self-luminescent display device, it requires a light source such as a backlight. The backlight is driven by an inverter, and consumes the most amount of power in the LCD.
Meanwhile, the inverter has a high voltage transformer to drive the backlight. The transformer functions to apply voltage to a lamp that constitutes an LCD panel by generating high AC output voltage with low AC input voltage.
The transformer resonates with the capacitance of the lamp and panel at the frequency applied to a primary side thereof, so that secondary voltage can be more increased than the turn ratio of primary and secondary windings. Therefore, the transformer may be referred to as a resonant transformer.
The transformer is generally manufactured by winding a primary coil at the low voltage side and a secondary coil at the high voltage side around a bobbin having a core inserted into a hollow portion thereof. One coil referred to as the primary coil is connected to an input circuit in which voltage is to be changed, and the other coil referred to as the secondary coil is connected to an output circuit in which the changed (transformed) voltage is used. When AC current of the input circuit passes through the primary coil, a magnetic field of which intensity and direction are changed is generated in response to the AC current. The change of magnetic flux induces AC voltage in the secondary coil, and the turn ratio of the primary and secondary coils determines a voltage transformation ratio.
A conventional transformer includes one bobbin having first and second coil winding portions around which primary and secondary coils are wound, respectively, a transformer cap into which the bobbin is inserted, and a pair of “” shaped cores respectively inserted into insertion holes formed in the bobbin by passing through both side portions of the transformer cap.
In the case of such a small-sized high voltage transformer, the winding turns of a coil at the high voltage side are considerably greater than those of a coil at the low voltage side, and hence the current that flows in the coil at the high voltage side is much less than the current that flows in the coil at the low voltage side. Therefore, the thickness of the coil at the high voltage side is much thinner than that of the coil at the low voltage side.
However, since the conventional transformer described above is used by winding the primary and secondary coils around only one bobbin, the primary and secondary coils are necessarily spaced apart from each other at a certain spacing distance so as to secure a creepage distance necessary for insulation, and therefore, the winding area of the primary coil is partially wasted. Further, since the bobbin is used to allow the primary and secondary coils to be wound therearound, there is a limitation in decreasing the height of the bobbin. Therefore, there is a limitation in slimming the transformer.